1. Field of the Invention
The present invention relates to an ophthalmic photography apparatus, and more particularly to an ophthalmic photography apparatus that can be used for non-mydriatic and mydriatic eye fundus color photography, visible light-excited fluorescence image photography, and infrared light-excited fluorescence image photography.
2. Description of the Prior Art
There are ophthalmic photography apparatuses such as fundus cameras and the like that, in addition to being capable of non-mydriatic and mydriatic color photography of the eye fundus, are also capable of photography by visible light-excited fluorescence (also designated as fluorescein angiography; FAG) and photography by infrared light-excited fluorescence (also designated as indocyanine green angiography; ICG). In each of these photographic modes, the apparatus is aligned and focused while observing the eye fundus, and the eye fundus is then photographed by operating a shutter switch.
The alignment and focusing prior to photography are done by projecting an alignment index and a focus index onto the eye to be examined and controlling the index light quantities according to the state of a photoelectric transducer receiving the image from the eye fundus (Japanese Laid Open Patent Publication No. 1987-41637), controlling the index brightness in accordance with the gain of an electronic camera (Japanese Laid Open Patent Publication No. 1997-66032), shielding the indexes during the fluorescence photography (Japanese Laid Open Patent Publication No. 1999-197113), shielding the indexes during photography (Japanese Laid Open Utility Model Publication No. 1993-102), or changing the wavelength of the observation light with the passing of the time during infrared light-excited fluorescence photography (Japanese Laid Open Patent Publication No. 2004-81255).
However, in the case of fundus cameras used to carry out infrared light-excited fluorescence photography in which a CCD is used for both observation and dynamic image photography, the focus index and alignment index that are not required for diagnosis are also recorded because the images that are observed are the same images that are recorded.
If, in order to avoid this problem, the indexes are not used during the infrared light-excited fluorescence photography, focusing and alignment have to be adjusted visually. Such visual adjustments may be possible during the initial phase when there is a sufficient level of infrared light-excited fluorescence, but become difficult in the later phase in which there is insufficient infrared light-excited fluorescence. Thus, during the transition from the initial to the later phase, the examiner has to switch the indexes on and off, using his or her own judgment, which increases the burden on the examiner when making a dynamic image recording.
It is therefore an object of the present invention to provide an ophthalmic photography apparatus that is able to carry out infrared light-excited fluorescence photography and recordings by securely enabling focusing and alignment adjustments to be made over the entire period of the infrared light-excited fluorescence photography.